1. Field of the Invention:
This invention relates to a microfilm handling system for retrieving from among a multiplicity of image information frames recorded on a microfilm a desired one and setting the retrieved frame in place at a projecting position.
2. Description of the Prior Art:
Generally, a microfilm is provided with a multiplicity of frames to which blip marks are affixed severally. A microfilm handling system which handles a microfilm of such a construction is provided with a sensor which, by virtue of its ability to discern the blip marks, serves the purpose of searching the multiplicity of frames on the microfilm and retrieving a desired frame out of them.
Among microfilm handling systems in popular use is counted a microfilm handling system of the type having a sensor for blip marks disposed inside a projected light path through which an image is projected. The system of this type has the advantage of allowing a light source which is primarily used for projection of an image to be additionally used the detection of the blip marks by the sensor and, in the meantime, suffers from the disadvantage that the sensor is prevented from clearly discerning blip marks when illuminance on the microfilm is varied for the image projection. For the purpose of enhancing a precision with which the detection of the marks is performed, adoption of a system of the type having the sensor and its own light source for the detection of marks disposed outside the projected light path may be conceived. In the system of this type, since the sensor obtains light from its own light source, it is enabled to detect the marks satisfactorily at all times.
Incidentally, in the system of the type having the sensor disposed outside the projected light path, the sensor is disposed on the microfilm feeding side relative to the position for the projection of an image for the sake of convenience of the conveyance of a microfilm. At the time that the mark of the frame being retrieved reaches the detecting position of the sensor, the corresponding frame falls on the location apart from the projected light path of an image. After the sensor has detected the mark corresponding to the retrieved frame, the microfilm is advanced by a distance equalling the interval between the sensor and the projected light path so that the retrieved frame will be set in the projected light path.
The technique of enabling a plurality of interrelated frames to be discerned as one group, batch or block out by changing the marks in size or position has been known to the art. In the case of a patent specification which consists of a plurality of pages, for example, the image frames of the microfilm containing the first through last pages of this patent specification are discerned as one batch or block. In the microfilm handling system which is capable of discerning the plurality of frames as one batch as described above, enabling the plurality of frames included in the one batch may be sequentially copied by a copying operation (Japanese Patent Publication 60-23,338 and Japanese Patent Publication 60-24,452).
In accordance with the reader printer disclosed in the patent publication mentioned above, when the plurality of frames in one batch are to be copied, the copying is started from the last frame and continued until the first frame, with the microfilm moved backwardly to successive intervening frames. By starting the copying from the last frame in this manner, the convenience in the handling of produced copies is notably augmented because the copies of the frames are piled up in sequence from the copy of the last frame on a discharge tray. Incidentally, the reader printer disclosed in these patent publications has the sensor for the detection of the blip marks disposed inside the projected light path.